Ignition fuse blowing

[kyleag89]

Ok guys.. I found a 96 XJ with 137K no rust and in great shape. The guy says that it starts and runs for a minute then the ignition fuse 60amp under the hood blows. Have any of you had this problem before? I'm thinking of buying it but the electrical problems on cars aggravate and confuse me! :nuts: O its a 4.0 auto

[kyleag89]

I just went and looked at the XJ. It is in great shape and I think I might have drooled a little. He had the steering column apart and a new ignition installed but no luck. As soon as it starts the 60A fuse for the ignition blew.

[Eagle]

I don't have a '96 but my immediate reaction is: WHAT 60-amp ignition fuse? I have never heard of a Cherokee being equipped with an ignition fuse. However, the '96 is a unique year, because it's the year when the factory sliced and diced the old wiring harness to implement OBD-II, but they did it as a kludge because they knew they were coming out with a new body style and new dashboard the following model year.

 

When you say it blows the fuse "as soon as it starts" ... is that what really happens? Does the engine actually start before the fuse blows? Or is there a fuse on the starter itself and it blows when the starter tries to crank the engine?

[kyleag89]

There is a 60A maxi fuse in the under hood fuse box, It says Ignition on it. The guy who owns it started it while I watched the fuse, it fired ran for about 2 seconds then I saw the fuse pop and then it shut off. If you look at a wiring diagram it is the fuse on the POS red wire coming from the batt to the fuse box then goes directly to the ignition switch.

 

BATT---------60Afuse--------Ignition I guess what I am trying to ask is.. If the wire itself is good from the fuse to the new ignition, then could it be a short somewhere in the circuit when in the RUN position? I would guess that the fuse is only blowing when the key is in the RUN position so therefore it would have to be something in that circuit. :hmm:

[Eagle]

There is a 60A maxi fuse in the under hood fuse box, It says Ignition on it. The guy who owns it started it while I watched the fuse, it fired ran for about 2 seconds then I saw the fuse pop and then it shut off. If you look at a wiring diagram it is the fuse on the POS red wire coming from the batt to the fuse box then goes directly to the ignition switch.

 

BATT---------60Afuse--------Ignition I guess what I am trying to ask is.. If the wire itself is good from the fuse to the new ignition, then could it be a short somewhere in the circuit when in the RUN position? I would guess that the fuse is only blowing when the key is in the RUN position so therefore it would have to be something in that circuit. :hmm:

I don't have a '96 wiring diagram, so I can't look at it. I'll take your word for it.

 

So if it starts okay and then pops the fuse after starting, your conjecture would appear to be spot on -- there must be a short somewhere in the RUN circuit that's being by-passed in the START circuit. But ... when you initially just turn the key to ON, that is the RUN position. The circuits are all connected the same, whether or not the engine is running. So if he just turns the key to RUN (but doesn't start the engine) ... does the fuse blow? If not, the answer must lie in what's different when the engine is actually running. The circuits are all connected the same ... the ONLY difference is that the alternator is producing electricity when the engine is running. So maybe the alternator or voltage regulator is bad?

[kyleag89]

Thank you Eagle but I just went to buy it about 2 hours ago and when I showed up a couple guys were loading it on there car dolly! :fs1: I can never catch a break!